From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on yquem.inria.fr X-Spam-Level: X-Spam-Status: No, score=0.0 required=5.0 tests=AWL autolearn=disabled version=3.1.3 X-Original-To: caml-list@yquem.inria.fr Delivered-To: caml-list@yquem.inria.fr Received: from discorde.inria.fr (discorde.inria.fr [192.93.2.38]) by yquem.inria.fr (Postfix) with ESMTP id F2C2FBC6B for ; Wed, 27 Jun 2007 11:11:02 +0200 (CEST) Received: from pih-relay04.plus.net (pih-relay04.plus.net [212.159.14.131]) by discorde.inria.fr (8.13.6/8.13.6) with ESMTP id l5R9B2N4001411 (version=TLSv1/SSLv3 cipher=AES256-SHA bits=256 verify=NO) for ; Wed, 27 Jun 2007 11:11:02 +0200 Received: from [80.229.56.224] (helo=beast.local) by pih-relay04.plus.net with esmtp (Exim) id 1I3TY9-00042C-LG for caml-list@yquem.inria.fr; Wed, 27 Jun 2007 10:10:57 +0100 From: Jon Harrop Organization: Flying Frog Consultancy Ltd. To: caml-list@yquem.inria.fr Subject: Re: [Caml-list] let rec and polymorphic functions Date: Wed, 27 Jun 2007 10:05:10 +0100 User-Agent: KMail/1.9.7 References: <000e01c7b896$d3372440$6a7ba8c0@treble> In-Reply-To: <000e01c7b896$d3372440$6a7ba8c0@treble> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200706271005.10837.jon@ffconsultancy.com> X-Miltered: at discorde with ID 468229A6.001 by Joe's j-chkmail (http://j-chkmail . ensmp . fr)! X-Spam: no; 0.00; ad-hoc:01 polymorphism:01 recursion:01 val:01 val:01 printf:01 ad-hoc:01 specifier:01 ocaml:01 ocaml:01 run-time:01 higher-order:01 recursive:01 recursion:01 recursive:01 There are many problems with this. Google for ad-hoc polymorphism, polymorphic recursion and generic printing. On Wednesday 27 June 2007 09:40:31 David Allsopp wrote: > out "TEST"; val out : string -> unit > out "%d" 0; val out : format -> int -> unit As printf is ad-hoc polymorphic, you must supply the format specifier immediately and OCaml will generate a custom printer for you. OCaml does not use run-time types so you cannot have a generic print function: you must specific print functions for each of your (possibly higher-order) types. Also, recursive calls ossify the function to a monomorphic type, so you cannot do polymorphic recursion in OCaml. There are workaround using recursive modules or objects but I don't think this is what you want here. -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. The OCaml Journal http://www.ffconsultancy.com/products/ocaml_journal/?e